Based on the analysis of soil aggregate content in runoff plots

the composition and distribution of black soil aggregates on sloping farmland with different slope degrees are discussed.Results show that both the content of large soil aggregates and the content of medium soil aggregates have significantly negative correlation with slope degree in 3°~18° plots.With slope degree increasing

geometric mean diameter(GMD)and mean weight diameter(MWD)decrease evidently

soil anti-erodibility decreases

and potential erosion risk increases.In 3°~6° plots

D_50 value for cross tillage is higher than that for no-tillage

but in the upper of 9° plot

D_50 value for cross tillage is higher and in the lower of 9° plot

D_50 value for no-tillage is higher.This indicates that cross tillage mode is beneficial to maintain the amount of black soil aggregates on gentle sloping farmland and soil in the lower of 9° plot under no-tillage has strong anti-erodibility.